Eyeglass lens

ABSTRACT

An aspect of the present invention relates to an eyeglass lens comprising a lens substrate and a vapor-deposited film either directly or indirectly on the lens substrate, wherein the vapor-deposited film is an oxide film of metal selected from the group consisting of zirconium and tantalum, with a proportion accounted for by regions observed in a streaky shape, in a columnar shape, or in a lump shape in a cross-sectional image of the vapor-deposited film obtained by a transmission electron microscope of equal to or less than 20%.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No.PCT/JP2013/076600 filed Sep. 30, 2013, claiming priority based onJapanese Patent Application Nos. 2012-217200, filed Sep. 28, 2012 and2012-217204, filed Sep. 28, 2012, the contents of all of which areincorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to an eyeglass lens, and moreparticularly, to an eyeglass lens having a vapor-deposited film that canexhibit good heat resistance (crack resistance) and scratch resistance.

BACKGROUND ART

Generally, eyeglass lenses are imparted with various properties byforming various functional films on the lens substrate while achieving adesired refractive index by means of the lens substrate. Antireflectivefilms imparting an antireflective property to the lens surface arewidely employed as such functional films. Among these, vapor-depositedfilms of zirconium (Zr) oxide are inexpensive among the high refractiveindex layers constituting multilayer antireflective films, and are thusconsidered advantageous in terms of cost (for example, see JapaneseUnexamined Patent Publication (KOKAI) No. 2009-193022, which isexpressly incorporated herein by reference in its entirety).Vapor-deposited films of tantalum (Ta) oxide can also function as highrefractive index layers in the same way as vapor-deposited films ofzirconium oxide.

Eyeglass lenses are required to have good durability that does notdeteriorate even when placed in various environments. For example,eyeglass lenses are sometimes worn in the bath, left in automobiles insummer, and worn by wearers who are active for extended periodsoutdoors. There is a need for them to maintain good quality withoutdeveloping cracks even when exposed to such elevated temperatures. Ineyeglass lenses having vapor-deposited films of zirconium oxide andtantalum oxide, cracks may develop in the vapor-deposited films atelevated temperatures, resulting in phenomena such as a drop in opticalcharacteristics and decreased adhesion between layers constituting themultilayer antireflective film.

Eyeglass lenses are also required to have good resistance to scratchingwithout developing scratches or cracks with the application of externalforces. Eyeglass lenses are subjected to various external forces in thecourse of removing fingerprints, debris, and other grime adhering to thelens surface. The scratches and cracks that develop due to such externalforces cause phenomena such as decreased optical characteristics in theeyeglass lens and diminished adhesion between layers constitutingmultilayer antireflective films.

SUMMARY OF THE INVENTION

An aspect of the present invention provides for an eyeglass lens havinga zirconium oxide or tantalum oxide vapor-deposited film and having goodheat resistance (crack resistance) and scratch resistance.

The present inventors discovered the following previously unknownmatters in the course of conducting extensive research into achievingthe above eyeglass lens:

(1) The greater the uniformity in the cross-sectional TEM image of theabove metal oxide vapor-deposited film, the better the heat resistanceand the fewer cracks generated at elevated temperatures;

(2) The greater the uniformity in the cross-sectional TEM image of theabove metal oxide vapor-deposited film, the greater the compressivestress, such that even when external forces were applied, forcescounteracting them were produced, resulting in good scratch resistanceand the generation of few scratches or cracks due to external forces.

The uniformity of the above cross-sectional TEM image is an indicator ofhigh uniformity and of low anisotropy in the sectional direction of theabove vapor-deposited film. That is, increasing uniformity and reducinganisotropy in the sectional direction makes it possible to improve theheat resistance and scratch resistance of the above vapor-depositedfilm, a fact discovered by the present inventors.

Based on the above discoveries, the present inventors used this newindicator in the form of the uniformity of the cross-sectional TEM imageand conducted repeated trial and error by varying the manufacturingconditions of the vapor-deposited films of the above metal oxides. Thisresulted in the discovery that the oxide film of a metal selected fromthe group consisting of zirconium and tantalum, in which the proportionaccounted for by regions observed in a streaky shape, in a columnarshape, or in a lump shape in a cross-sectional TEM image was equal to orless than 20%, had good scratch resistance and high heat resistance ofno (or extremely few) cracks generated even when placed at hightemperature. The present invention was devised on that basis.

An aspect of the present invention relates to an eyeglass lenscomprising a lens substrate and a vapor-deposited film either directlyor indirectly on the lens substrate, wherein

the vapor-deposited film is an oxide film of metal selected from thegroup consisting of zirconium and tantalum, with a proportion accountedfor by regions observed in a streaky shape, in a columnar shape, or in alump shape in a cross-sectional image of the vapor-deposited filmobtained by a transmission electron microscope of equal to or less than20%.

In an embodiment, the average grain size of the vapor-deposited filmobserved in a planar image obtained by a transmission electronmicroscope is equal to or greater than 5 nm.

In an embodiment, in the above vapor-deposited film, the proportionaccounted for by grain boundaries, which are boundaries separatinggrains from regions outside of the grains, in a planar image obtained bya transmission electron microscope is less than 10%.

In an embodiment, the above vapor-deposited film is a zirconium oxidefilm.

In an embodiment, the above eyeglass lens comprises the abovevapor-deposited film as at least one layer in a multilayervapor-deposited film.

A further aspect of the present invention relates to a method ofdetermining a manufacturing condition of an eyeglass lens comprising avapor-deposited film that is an oxide film of metal selected from thegroup consisting of zirconium and tantalum, which comprises:

determining a candidate vapor deposition condition to be employed invapor deposition of the vapor-deposited film in actual manufacturing;

forming a test vapor-deposited film by conducting vapor deposition underthe candidate vapor deposition condition that has been determined; and

taking at least one TEM image selected from the group consisting of aplanar TEM image or a cross-sectional TEM image the test vapor-depositedfilm that has been formed and determining a vapor deposition conditionof the vapor-deposited film in actual manufacturing, with adetermination standard that the higher the uniformity of the TEM image,the more likely the candidate condition is to be a vapor depositioncondition capable of forming a vapor-deposited film exhibiting good heatresistance or good scratch resistance, or good heat resistance and goodscratch resistance.

In an embodiment, the uniformity is determined according to at least onedetermination standard selected from the group consisting of standards 1to 4 below:

standard 1: in a cross-sectional TEM image, the lower the proportionaccounted for by regions observed in a streaky shape, in a columnarshape, or in a lump shape, or the smaller the regions, the higher theuniformity is determined to be;

standard 2: the greater the area of dark portions obtained by binaryprocessing of a cross-sectional TEM image obtained as a bright-fieldimage, or the greater the area of the bright portions obtained by binaryprocessing of a cross-sectional TEM image obtained as a dark-fieldimage, the higher the uniformity is determined to be;standard 3: the lower the proportion accounted for by grain boundariesin a planar TEM image, the higher the uniformity is determined to be;andstandard 4: the greater the grain size observed in a planar TEM image,the higher the uniformity is determined to be.

A further aspect of the present invention relates to a method ofmanufacturing an eyeglass lens, which comprises:

determining a manufacturing condition by the method set forth above; and

conducting vapor deposition under the manufacturing condition that hasbeen determined to form a vapor-deposited film in the form of an oxidefilm of metal selected from the group consisting of zirconium andtantalum.

In an embodiment, the above vapor-deposited film is formed as a layerconstituting a multilayer antireflective film.

An aspect of the present invention can provide an eyeglass lens havinggood durability in which the generation of cracks in the vapor-depositedfilm—which is an oxide film of metal selected from the group consistingof zirconium and tantalum—at high temperature and the occurrence ofscratches and cracks due to external forces are inhibited.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 A descriptive drawing of a method of measuring film stress.

FIG. 2 A descriptive drawing of a method of measuring film stress.

FIG. 3 is a cross-sectional TEM image obtained for Example 1.

FIG. 4 is a planar TEM image obtained for Example 1.

FIG. 5 is a cross-sectional TEM image obtained for Example 2.

FIG. 6 is a planar TEM image obtained for Example 2.

FIG. 7 is a cross-sectional TEM image obtained for Example 3.

FIG. 8 is a planar TEM image obtained for Example 3.

FIG. 9 is a planar TEM image obtained for Comparative Example 1.

FIG. 10 is a cross-sectional TEM image obtained for Comparative Example2.

FIG. 11 is a planar TEM image obtained for Comparative Example 2.

FIG. 12 is a partial enlargement within a frame of the grain of theplanar TEM image shown in FIG. 11.

MODES FOR CARRYING OUT THE INVENTION

An aspect of the present invention relates to an eyeglass lenscomprising a lens substrate and a vapor-deposited film either directlyor indirectly on the lens substrate, wherein the vapor-deposited film isan oxide film of metal selected from the group consisting of zirconiumand tantalum, with a proportion accounted for by regions observed in astreaky shape, in a columnar shape, or in a lump shape in across-sectional image of the vapor-deposited film obtained by atransmission electron microscope (cross-sectional TEM image) of equal toor less than 20%.

The eyeglass lens according to an aspect of the present invention willbe described in greater detail below.

The eyeglass lens has a vapor-deposited film in the form of an oxidefilm of metal selected from the group consisting of zirconium andtantalum, either directly or indirectly on the lens substrate. Thezirconium oxide film will be denoted as a “Zr oxide film” and thetantalum oxide film as a “Ta oxide film” hereinafter. The lens substrateis not specifically limited. Materials that are commonly employed as thelens substrates of eyeglass lenses, such as materials selected fromamong polyurethane, polythiourethane, polycarbonate, diethyleneglycolbisallylcarbonate, other plastics, and inorganic glass, can be employed.The thickness and diameter of the lens substrate are normally athickness of about 1 to 30 mm and a diameter of about 50 to 100 mm, butthere is no specific limitation.

As set forth above, Zr oxide films and Ta oxide films can function ashigh refractive index layers. They can be used to form a single layer onthe lens substrate, or combined with layers of different refractiveindexes, such as a low refractive index layer formed primarily of SiO₂to form multilayer vapor-deposited films provided in the lens substrate.Such multilayer vapor-deposited films can further contain single-layeror two or more vapor-deposited films (also called “electricallyconductive oxide layers”) formed by vapor deposition using vapordeposition sources primarily comprised of an electrically conductiveoxide. Providing such an electrically conductive oxide layer can preventthe adhesion of dust and debris on the lens surface. The electricallyconductive oxide is desirably in the form of a known indium oxide, tinoxide, or zinc oxide, or some compound oxide thereof, that is known as atransparent electrically conductive oxide so as not to reduce thetransparence of the eyeglass lens. From the perspective of transparenceand electrical conductivity, a preferred example of an electricallyconductive oxide is an indium-tin oxide (ITO). An embodiment of themultilayer vapor-deposited film is an antireflective film. However,there is no limitation to antireflective films. Any such layer thatfunctions as a reflecting layer (cutting layer) performing the functionof reducing the amount of light entering the eye of the eyeglass wearerby selectively reflecting light of a prescribed wavelength range willdo. An example of light that is desirably reflected is ultravioletlight. The short wavelength light known as blue light that is emitted bythe liquid crystal monitors that have become widespread in recent years,particularly the light emitted at a wavelength of roughly 400 nm to 500nm by LED liquid-crystal monitors, is another example.

The thickness of the Zr oxide or Ta oxide film can be a physical filmthickness of about 10 to 100 nm, for example. It suffices to determinethe film thickness based on the function (antireflective property or thelike) that is required of the film; there is no specific limitation. Thefilm thicknesses given below refer to physical film thicknesses.

The eyeglass lens according to an aspect of the present inventioncomprises one or more layers of Zr oxide film or Ta oxide film on a lenssubstrate. These oxide films can be optionally combined into two or morelayers. At least one layer of Zr oxide film or Ta oxide film is avapor-deposited film having a proportion accounted for by regionsobserved in a streaky shape, in a columnar shape, or in a lump shape ina cross-sectional TEM image of equal to or less than 20%. Thecross-sectional TEM image is obtained by observing the vapor-depositedfilm that is the subject of observation by a transmission electronmicroscope (TEM) in a direction parallel or approximately parallel tothe direction of thickness. By contrast, the method of observation in adirection that is perpendicular to, or approximately perpendicular to,the direction of thickness is planar TEM observation. This point will bedescribed further below. Through research, the present inventorsdiscovered that the higher the uniformity of the cross-sectional TEMimage, the greater the heat resistance (crack resistance) and scratchresistance. The occupancy rate of regions observed in a streaky shape,in a columnar shape, or in a lump shape in the cross-sectional TEM imageis adopted as an indicator of uniformity in an aspect of the presentinvention. Based on investigation conducted by the present inventors, inelemental analysis conducted by TEM-EDS, for example, no cleardifference was observed between films with different heat resistance(crack resistance) and scratch resistance for Zr oxide films and Taoxide films. Thus, the specific correlation between the heat resistance(crack resistance) and scratch resistance of Zr oxide films and Ta oxidefilms of different uniformity in their cross-sectional TEM images wasdiscovered by the present inventors. The cross-sectional TEM image isobtained in the present invention by known methods in which atransmission electron microscope is employed.

The regions observed in a streaky shape, in a columnar shape, or in alump shape in the cross-sectional TEM image are observed as regionsdistinguished from the other regions by different shades in across-sectional TEM image obtained at a magnification of 50,000 to400,000-fold. Normally, these regions are observed with a nonuniform,marbled structure in a cross-sectional TEM image. The proportion of thetotal area of the observed field accounted for by these regions iswithin the above range. It suffices to set the observed field to permitclear determination by distinguishing between the above regions andother regions by different shades, based on the size of the regionsobserved in a streaky shape, in a columnar shape, or in a lump shape inthe cross-sectional TEM image. The observed field can be set to within arange of, for example, 50 nm square (50 nm×50 nm) to 150 nm square (150nm×150 nm). As an example, the observed field at a magnification of100,000 to 200,000-fold can be set to from 100 nm square (100 nm×100 nm)to 150 nm square (150 nm×150 nm). At a magnification exceeding200,000-fold, the observed field can be set to from 50 nm square (50nm×50 nm) to 100 nm square (100 nm×100 nm). It is desirable to changethe observation position and take TEM images at five or more spots (suchas 5 to 10 spots) and calculate the arithmetic average of the valuesmeasured in each of the TEM images to obtain the occupancy rate of theregions observed in a streaky shape, in a columnar shape, or in a lumpshape in the cross-sectional TEM image. A Zr oxide film or Ta oxide filmin which the proportion of the regions accounted for that is thuscalculated is equal to or less than 20% will afford high heat resistanceand good scratch resistance. This was discovered for the first time everbased on the results of extensive research conducted by the presentinventors. The proportion accounted for by these regions is desirablyequal to or less than 15%, preferably equal to or less than 10%, andmore preferably, equal to or less than 5%. The proportion accounted forby the regions in a lump shape is desirably kept low. Obtaining TEMimages at five or more spots (for example, 5 to 10 spots) by varying theobservation position and averaging the values measured for each TEMimage is desirable to obtain the proportion accounted for by theseregions.

The cross-sectional TEM image can be obtained as a bright-field image oras a dark-field image. From the perspective of facilitating analysis,the cross-sectional TEM image is desirably obtained in the form of adark-field image for those containing microcrystals. On the other hand,when considerable amorphous materials are present, the cross-sectionalTEM image is desirably obtained as a bright-field image.

The above regions observed in the cross-sectional TEM image are, as setforth above, observed in a streaky shape, in a columnar shape, or in alump shape, and may be indeterminate forms. Examples of specificstructures that can be contained in these regions are columnarstructures and crystalline grains. Columnar structures are mainlydetermined in a direction normal to, or approximately normal to, thesurface of the lens substrate (base material). Crystalline grains aremainly determined as grains or in a state in which they are arranged incolumns in a direction normal to, or approximately normal to, the lenssubstrate. The term “in a direction approximately normal to” is used tomean including directions inclined by about ±20° when the normaldirection is denoted as 0°. Columnar structures and crystalline grainsmay include amorphous materials in addition to crystals. Theincorporation of crystals can be determined by the observation of thecrystal lattice in the TEM image.

In a desirable embodiment, in the Zr oxide film and Ta oxide film, theaverage size of grains (also referred to as the “average grain size”hereinafter) observed in a planar image (planar TEM image) obtained by atransmission electron microscope is equal to or greater than 5 nm. Thisaverage grain size is preferably equal to or greater than 5.5 nm, morepreferably equal to or greater than 5.8 nm. The average grain size is,for example, equal to or less than 20 nm. However, the presence of largenumbers of micrograins diminishes the uniformity of the film, so thegrain size is desirably as large as possible. In another desirableembodiment, the proportion accounted for by grain boundaries, which areboundaries separating grains from regions outside of the grains, in aplanar TEM image is less than 10%, preferably equal to or less than 5%,and more preferably, equal to or less than 3%. The smaller, the better.

The grains that are observed in the planar TEM image are observed asregions that are enclosed by grain boundaries and thus separated fromother regions in a planar TEM image obtained at a magnification of50,000 to 400,000-fold. The grain boundaries can be identified bydifferences in shading in the TEM image. The proportion of the entirearea of the observed field that is accounted for by grain boundariesdesirably falls within the range stated above. The average grain sizealso desirably falls within the range stated above. It suffices to setthe observed field so as to permit a clear determination of thedistinction between the grains and regions outside the grains by thegrain boundaries, based on the grain size observed in the planar TEMimage.

The grains that are observed in the planar TEM image are distinguishedfrom other regions by the grain boundaries, and are primarily regionsdetermined to be granular or in a cluster shape, but can also be ofindeterminate shape. Examples of the specific structures of the grainsare structures within which crystalline grains are present in thegrains. The grains can contain one or both of crystals and amorphousmaterials. The presence of crystals can be determined by observing thecrystal lattice. The average grain size in the planar TEM image that isreferred to can be either a value that is calculated by measuring themajor axis and minor axis of each region distinguished as another regionby the grain boundaries in the observed field, calculating the averagevalue of the major axes and the average value of the minor axes of thelump regions contained in the observed field, and adopting the valueobtained by calculating (major axis average value+minor axis averagevalue)/2. Alternatively, the diameter of a circle having the same areaas each of the regions, that is, the equivalent circle diameter, iscalculated for the grains that are contained in the observed field, andthe average value is adopted as the average grain size. Grains withportions that protrude from the image are not measured. The averagevalue is the arithmetic average. When numerous grains are observed, thearea of the observed field can be changed to contain 50 or more(desirably 100 or more) grains, for example. When indeterminate grainsare contained, in cases where their shapes are small or theircrystallinity is high, the observation region can be expanded (forexample, a 100,000-fold field can be expanded to a 200% image) andcompared with results obtained from an observation image that has beenseparately observed at high magnification (for example, 200,000-fold,250,000-fold, or 400,000-fold). When the value of the results ofcomparison differs by 1 nm or more, the average value is desirablyadopted.

Reference can be made to JIS R 1670: 2006 for measurement of the averagegrain size set forth above.

As described above with regard to observation of the cross-sectional TEMimage, the grain boundary occupancy rate and average grain size aredesirably obtained as arithmetic averages calculated at five or morespots (for example, 5 to 10 spots) by changing the observation position.The details of obtaining and analyzing the planar TEM image areidentical to those in the description given for the cross-sectional TEMimage above.

The planar TEM image can be obtained as a bright-field image or as adark-field image. From the perspective of ease of analysis, it isdesirable to obtain a planar TEM image in the form of a dark-field imagewhen microcrystals are contained. Conversely, it is desirable to obtainthe planar TEM image in the form of a bright-field image whenconsiderable amorphous materials are present.

Desirably, the above-described Zr oxide film can be formed by vapordeposition of a vapor deposition source the primary component of whichis ZrO₂ and the Ta oxide film can be formed by vapor deposition of avapor deposition source the primary component of which is Ta₂O₅. In anaspect of the present invention, the “primary component” refers to thecomponent accounting for the greatest portion of the vapor depositionsource or the vapor deposition layer. This component normally accountsfor about 50 mass percent to 100 mass percent of the total, even about90 mass percent to 100 mass percent. Impurities that inevitably mix intrace amounts will sometimes be contained in the vapor depositionsource. Other components can be contained in ranges that do notcompromise functioning of the primary component, such as other inorganicsubstances and known additive components that play assisting roles invapor deposition. Vapor deposition can be conducted by vacuum vapordeposition, ion plating, plasma CVD, the ion-assisted method, reactivesputtering, or the like. The ion-assisted method is desirable forobtaining good adhesion.

For example, in the ion-assisted method, it is possible to control thephysical properties of the vapor-deposited film that is formed by meansof the vapor deposition conditions, such as the degree of vacuum,acceleration voltage, acceleration current, assist gas (ionized gas)flow rate and blending ratio during vapor deposition, as well as thecomposition and the like of the vapor deposition source employed. In anembodiment of the present invention, the vapor deposition conditions canbe determined by conducting preliminary testing as needed to form theabove Zr oxide film and Ta oxide film.

In the field of manufacturing eyeglass lenses, to stably provideeyeglass lenses of a quality that does not decrease over time, prior todetermining the conditions used in actual manufacturing, it is commonpractice to conduct accelerated durability testing on test sampleeyeglass lenses that have been fabricated using candidate manufacturingconditions and adopt, in actual manufacturing, manufacturing conditionsthat are identical to the manufacturing conditions of the test sampleeyeglass lenses that have exhibited good test results. For example, byforming vapor-deposited films in actual manufacturing undermanufacturing conditions that have yielded test sample eyeglass lenseswith few cracks in accelerated durability testing by oven heating, it ispossible to obtain eyeglass lenses exhibiting good durability withoutundergoing deterioration of the vapor-deposited film over extendedperiods of actual use.

Further, to stably provide high-quality eyeglass lenses, prior todetermining conditions for actual manufacturing, it is common practiceto conduct performance evaluation tests on test sample eyeglass lensesfabricated under candidate manufacturing conditions and adoptmanufacturing conditions identical to the manufacturing conditions oftest sample eyeglass lenses exhibiting good test results in actualmanufacturing. For scratch resistance, by forming vapor-deposited filmsin actual manufacturing by manufacturing conditions that have yieldedtest sample eyeglass lenses producing few cracks in scratch tests inwhich loads are placed on steel wool or a sand eraser, for example, itis possible to obtain eyeglass lenses exhibiting good durability withlittle scratch or crack generation in actual use.

Although the above accelerated durability test has become indispensableto providing eyeglass lenses exhibiting good durability for extendedperiods and with high reliability, in order to manufacture eyeglasslenses that currently pass accelerated durability tests, candidate vapordeposition conditions are determined for manufacturing product eyeglasslenses, eyeglass lenses are fabricated by forming vapor deposition filmsunder the vapor deposition conditions that have been determined, and theeyeglass lenses that have been fabricated are subjected to accelerateddurability testing. When the evaluation standards are not satisfied, newcandidate vapor deposition conditions are selected and the series ofsteps are repeated in a process of trial and error. Even though thescratch resistance test employing test sample eyeglass lenses set forthabove has become indispensable for providing eyeglass lenses exhibitinggood scratch resistance over extended periods with high reliability, inorder to manufacture eyeglass lenses that currently pass scratchresistance tests, candidate vapor deposition conditions are determinedfor manufacturing product eyeglass lenses, eyeglass lenses arefabricated by forming vapor deposition films under the vapor depositionconditions that have been determined, and the eyeglass lenses that havebeen fabricated are subjected to scratch resistance testing. When theevaluation standards are not satisfied, new candidate vapor depositionconditions are selected and the series of steps are repeated in aprocess of trial and error.

By contrast, by conducting evaluation based on a TEM image selected fromthe group consisting of the cross-sectional TEM image and the planar TEMimage in the manner discovered by the present inventors, manufacturingconditions for Zr oxide films and Ta oxide films, in which thegeneration under high temperatures can be inhibited and good scratchresistance can be achieved, can be readily discovered.

In an embodiment, candidate vapor deposition conditions for avapor-deposited film are first determined for the manufacturing of aproduct lens. For example, when using the ion-assisted method in actualmanufacturing, the above various conditions are determined. When usingsome other vapor deposition method, the various conditions relating tothat vapor deposition method are determined.

Next, vapor deposition is conducted under the vapor depositionconditions that have been determined as set forth above and a test vapordeposition film is fabricated. The test vapor deposition film can beformed on the lens substrate or on the surface of a functional film onthe lens substrate in the same manner as in actual manufacturing, orformed on a test substrate of glass or the like. From the perspective ofease of TEM observation, it is desirable to fabricate the test vapordeposition film on a glass substrate.

The test vapor deposition film fabricated as set forth above is observedby TEM selected from the group consisting of planar TEM observation andcross-sectional TEM observation. The details of the TEM observation areas set forth above.

In determining the uniformity of a cross-sectional TEM image, forexample, cross-sectional TEM images are visually compared. Images inwhich marbled nonuniform structures are found are determined to pooruniformity and images in which such structures are not found aredetermined to be highly uniform.

Uniformity can be determined based on standard 1, standard 2, orstandards 1 and 2 below.

Standard 1: in a cross-sectional TEM image, the lower the proportionaccounted for by regions observed in a streaky shape, in a columnarshape, or in a lump shape, or the smaller the regions, the higher theuniformity is determined to be.

Standard 2: the greater the area of dark portions obtained by binaryprocessing of a cross-sectional TEM image obtained as a bright-fieldimage, or the greater the area of the bright portions obtained by binaryprocessing of a cross-sectional TEM image obtained as a dark-fieldimage, the higher the uniformity is determined to be.

As an example of the regions observed in a streaky shape, in a columnarshape, or in a lump shape in evaluation by standard 1, in across-sectional TEM image obtained at a magnification of 150,000-fold,the region the major diameter (major axis length) of which based ondifferences in shading is equal to or greater than 1 nm as an actualsize is identified as the above region, and the presence of such regionscan be determined. The size of the above regions can be determinedmanually by a person or determined automatically by software analysis.For example, the determination of standard 1 can be conducted based onthe major axis length and minor axis length of one or more such regions(with a columnar structure, for example) in a cross-sectional TEM image,or based on the average value of the size of multiple such regions.

The binary processing of standard 2 can be conducted in the mannerbelow, for example.

The brightness of each pixel (picture element) of a cross-sectional TEMimage that has been obtained and the average brightness of the entireimage are obtained. The ratio of the number of pixels that are brighterthan the average relative to the entire number of pixels is adopted asthe area fraction of the bright portion, and the ratio of the number ofpixels that are darker than the average relative to the entire number ofpixels is adopted as the area fraction of the dark portion, and the areaof the bright portion and the dark portion can be obtained. Morespecifically, the gradation of each pixel is obtained for a commondigital image file (gray scale, for example, 256 gradations), ahistogram is prepared from the number of pixels and the gradation, andthe average gradation of the image as a whole is obtained. Binaryprocessing is conducted with the average gradation as a threshold, withpixels with gradations (bright) greater than or equal to the thresholdbeing assigned the value 1 and pixels with gradations (dark) below thethreshold being assigned the value 0. For the entire number of pixels,the number of pixels with a value of 1 is calculated, and this number isadopted as the bright area fraction.

Such binary processing can be automatically carried out with knownanalysis software.

The uniformity of a planar TEM image can be determined by, for example,comparing the analysis results of planar TEM images visually or withanalysis software, determining that those images in which the proportionaccounted for by grain boundaries is large are of poor uniformity, anddetermining that those images in which this proportion is small are ofhigh uniformity (standard 3). The larger the grain size observed in aplanar TEM image, the higher the uniformity is determined to be(standard 4). The grain size used in making the determination can bemeasured manually by a person or automatically with analysis software.

As set forth further below, the difference in uniformity of TEM imagesdetermined as set forth above correlates with the heat resistance (crackresistance) of the vapor-deposited film. The present inventors haveconfirmed that the higher the uniformity, the less cracking occurs atelevated temperatures. Accordingly, in an embodiment, the vapordeposition conditions of the vapor-deposited film in actualmanufacturing are determined based on a standard of determining thatcandidate conditions of high uniformity in a TEM image are vapordeposition conditions permitting the formation of a vapor-deposited filmexhibiting good heat resistance.

As set forth further below, the present inventors have confirmed thatthe difference in uniformity of TEM images determined as set forth abovecorrelates with the magnitude of compressive stress on thevapor-deposited film. The higher the uniformity, the greater thecompressive stress, such that even when external forces are applied, aforce counteracting them is generated, resulting in good scratchresistance. Accordingly, in an embodiment, the vapor depositionconditions for the vapor-deposited film in actual manufacturing aredetermined based on a standard of determining that candidate conditionsof high uniformity in a TEM image are vapor deposition conditions thatpermit the formation of a vapor-deposited film exhibiting good scratchresistance.

For example, in a specific implementation mode, it is possible todetermine actual manufacturing conditions based on a relativedetermination of adopting vapor deposition conditions for avapor-deposited film in actual manufacturing in the form of theconditions with the highest uniformity in their TEM images among two ormore sets of candidate conditions.

Further, in another specific implementation mode, preliminary testing isconducted, and a data base is created of correlations between vapordeposition conditions of vapor-deposited films and the tendency forcracks to develop at high temperature and the tendency for scratches andcracks to develop due to external forces. Based on the data base, auniformity threshold (critical value) permitting the formation ofvapor-deposited films with good heat resistance and scratch resistanceis set. Films having uniformity higher than or equal to the thresholdcan then be used to determine the vapor deposition conditions ofvapor-deposited films in actual manufacturing. The grain size or grainboundary occupancy rate in a planar TEM image, the bright portion ordark portion area fraction obtained by binary processing in across-sectional TEM image, the major axis length or minor axis length ofthe above regions, or the like can be employed as the threshold.

For example, for a cross-sectional TEM image, the area fraction of thedark portion in a bright-field image, or the area fraction of the brightportion in a dark-field image, can be set to equal to or greater than90%, even equal to or greater than 95%, of the entire analysis region asa uniformity determination standard permitting the formation ofvapor-deposited films with good heat resistance. A major axis length ofequal to or less than 5 nm and a minor axis length of equal to or lessthan 1 nm as the actual size of the above region observed in across-sectional TEM image obtained at a magnification of 150,000-foldcan be made a uniformity determination standard permitting the formationof vapor-deposited films of good heat resistance.

In yet another specific implementation mode, vapor depositionconditions, that have been changed (by changing the degree of vacuum,for example) so as not to affect the heat resistance or to increase theheat resistance from candidate vapor deposition conditions determined topermit the formation of a vapor-deposited film of good heat resistanceand scratch resistance based on the above relative determination resultsor the determination results based on the threshold, can be adopted asthe vapor deposition conditions in actual manufacturing.

It is possible to obtain an eyeglass lens having a Zr oxide film or a Taoxide film exhibiting good heat resistance and scratch resistancewithout having to go through the trial and error of accelerateddurability testing or scratch resistance testing using test sampleeyeglass lenses by determining the vapor deposition conditions of thevapor-deposited film in actual manufacturing based on the uniformityobserved in a TEM image.

A further aspect of the present invention provides a method ofmanufacturing an eyeglass lens comprising determining the manufacturingcondition by the above manufacturing condition determination method, andconducting vapor deposition based on the manufacturing condition thathave been determined to form a vapor-deposited film in the form of anoxide film of metal selected from the group consisting of zirconium andtantalum.

As set forth above, it is possible to determine vapor depositionconditions permitting the forming of a Zr oxide film or Ta oxide filmhaving good heat resistance (crack resistance) and scratch resistance bythe above method of determining the manufacturing condition. Thus, it ispossible to manufacture an eyeglass lens having a Zr oxide film or a Taoxide film exhibiting good durability in which the generation of cracksat elevated temperature as well as the generation of scratches andcracks due to external forces have been inhibited by forming thevapor-deposited film based on the manufacturing condition determined bythis method.

The above vapor-deposited film or a multilayer vapor-deposited filmcontaining it can be formed directly on a lens substrate or can beformed over a functional film such as a hard coat layer provided on thelens substrate. With the exception of conducting vapor deposition underthe film-forming condition permitting the formation of theabove-described Zr oxide film or Ta oxide film, known techniques can beapplied without limitation to manufacture the eyeglass lens according toan aspect of the present invention.

EXAMPLES

The present invention will be described below based on Examples.However, the present invention is not limited to the embodiments givenin Examples. The vapor deposition sources consisting of, withoutconsideration of impurities that might be potentially, or inevitably,mixed in, oxides that have been described were used below.

Examples 1 to 3, Comparative Example 1

A ZrO₂ vapor-deposited film was formed on one side of a lens substrate(Eyry made by HOYA Corp., refractive index 1.70) in a vapor depositiondevice at a vacuum of 4.3E-3 Pa using ZrO₂ as the vapor depositionsource by an ion-assisted method while introducing a 20 sccm quantity ofO₂ or a mixed gas of O₂/Ar as the assist gas. In each of Examples andComparative Examples, the ion gun conditions were varied betweenelectric currents of 100 to 300 mA and voltages of 100 to 500 V. Thefilm thickness calculated based on the film formation conditions wasabout 70 nm. The current and voltage of the ion gun were set in thefollowing sequence, in decreasing order: Example 1>Example 2>Example3>Comparative Example 1.

Comparative Example 2

With the exception that vapor deposition was conducted without an ionassist, a ZrO₂ vapor-deposited film was formed in the same manner asthat set forth above.

In the various Examples and Comparative Examples, multiple eyeglasslenses were fabricated as samples for the following evaluation.

<Evaluation Methods>

1. Proportion Accounted for by Regions Observed in a Streaky Shape, in aColumnar Shape, or in a Lump Shape in Cross-Sectional TEM Image

A sample was cut out of the ZrO₂ vapor-deposited film in a sectionaldirection for each of the ZrO₂ vapor-deposited films fabricated inExamples and Comparative Examples, etching by ion milling was used toshave down the ZrO₂ vapor-deposited film in the sectional direction, andthe etching was ended when the thickness of the ZrO₂ vapor-depositedfilm had been shaved down to about 100 nm. The sample thus fabricatedwas introduced into a transmission electron microscope and across-sectional TEM image (bright-field image) was obtained at amagnification of 150,000-fold. Cross-sectional TEM images were obtainedin five spots by changing the position with an observed field of 100nm×100 nm. For each Example and Comparative Example, the proportion ofthe total area of the observed field accounted for by regions observedin a streaky shape, in a columnar shape, or in a lump shape (regionsdistinguished from other regions by differences in shading, primarily inwhich marbling was observed) was calculated by commercial analysissoftware. The arithmetic average of the values calculated for five spotswere adopted as the proportion accounted for by the above regions.

2. Proportion Accounted for by Grain Boundaries Observed in Planar TEMImages

A portion of the lens substrate was shaved down by etching by ionmilling from the rear side relative to the side on which the ZrO₂vapor-deposited film had been formed. The etching was halted when theZrO₂ vapor-deposited film had been shaved down to a thickness of about20 nm. The sample thus fabricated was introduced into a transmissionelectron microscope and a planar TEM image (dark-field image) wasobtained at a magnification of 100,000-fold. Planar TEM images wereobtained in five spots by varying the position with an observed field of150 nm×150 nm. For each Example and Comparative Example, the proportionof the total area of the observed field accounted for by grainboundaries was calculated with commercial analysis software, and thearithmetic average of the values calculated for the five spots wascalculated as the proportion accounted for by grain boundaries.

3. Average Grain Size Observed in Planar TEM Image

The average grain size in the planar TEM images obtained in 2. above wasobtained by the method set forth above.

4. Evaluation of Heat Resistance

The eyeglass lenses fabricated in Examples and Comparative Examples wereplaced for two hours in a heating furnace at internal furnacetemperatures of 80° C., 90° C., and 100° C., observed under fluorescentlamps for the presence of cracks of several cm or more in length in thevapor-deposited film, and evaluated for heat resistance on the followingscale:

A: No cracks observed at any temperature;

B: Cracks observed at 100° C., but no cracks observed at 80° C. or 90°C.;

C: Cracks observed at 90° C. and 100° C., but no cracks observed at 80°C.;

D: Cracks observed at all temperatures.

5. Evaluation of Scratch Resistance

A water-repellent layer in the form of a fluorine-substituted alkylgroup-comprising organic silicon compound made by Shin-Etsu ChemicalCo., Ltd., KY130, was employed as vapor deposition source and vapordeposition was conducted by halogen heating on each of thevapor-deposited films of the eyeglass lenses fabricated in Examples andComparative Examples to fabricate samples.

The samples that had been fabricated were subjected to a scratchresistance test in which steel wool was run back and forth 20 timesunder a load of 2 kg or 3 kg. The vapor-deposited film was observedunder a fluorescent lamp following the scratch resistance test, thepresence of scratches and cracks 5 mm or greater in length was checkedfor, and the scratch resistance was evaluated on the following scale:

A: No scratches or cracks found at loads of 2 kg or 3 kg;

B: Scratches or cracks found at a load of 3 kg but no scratches orcracks found at a load of 2 kg;

C: Scratches and cracks observed at loads of 2 kg and 3 kg, with thenumber of scratches and cracks being equal to less than 5 but equal toor more than 2;

D: Scratches and cracks observed at loads of 2 kg and 3 kg, with thenumber of scratches and cracks being equal to or more than 6.

6. Evaluation of Film Stress

Heat resistance tape measuring 5 to 8 mm×30 to 40 mm in size was adheredto the surface of a piece of round platelike monitor glass (70 mm indiameter) that had been cleaned in a cleaning apparatus. As indicated inthe schematic of FIG. 1, a platelike cover glass (also referred to asthe “substrate” hereinafter) was placed on the surface of the monitorglass. To prevent adhesion to the monitor glass, one edge was disposedon the above heat-resistant tape, after which the edge portion of thecover glass was secured with heat resistant tape. The monitor glass withcover glass was placed in a vapor deposition device, and under the sameconditions as in the various Examples and Comparative Examples, a ZrO₂vapor-deposited film was formed on the surface of the cover glass.

Following film formation, the cover glass was removed from the monitorglass, and with one edge secured as shown in FIG. 2, the amount ofdisplacement from the horizontal surface was measured. The Stoneyequation, indicated below, was used to obtain the film stress σ.Negative values indicate compressive stress while positive valuesindicate tensile stress.

$\sigma = \frac{{Es} \cdot {ts}^{2} \cdot d}{3{\left( {1 - {vs}} \right) \cdot L^{2} \cdot {tf}}}$

In the equation, Es: Young's modulus of substrate; ts: thickness ofsubstrate; vs: Poisson ratio of substrate; L: length of substrate; tf:thickness of vapor-deposited film; d: amount of displacement

Table 1 gives the results of the above.

TABLE 1 Cross-sectional TEM image Proportion accounted for by regionsobserved in a Planar TEM image streaky shape, Proportion in a columnaraccounted Average Evaluation results shape, or in a for by grain grainsize Heat Scratch Film stress lump shape boundaries (nm) resistanceresistance (MPa) Ex. 1 2 1 11.5 A A −200 Ex. 2 10 3 8.2 B A −100 Ex. 315 5 5.8 C B 50 Comp. 30 10 3.5 D D 100 Ex. 1 Comp. 55 15 3.1 D D 150Ex. 2

Based on the results shown in Table 1, an aspect of the presentinvention can be determined to provide eyeglass lenses having a Zr oxidefilm with high heat resistance withstanding high temperatures of 80° C.and above and good scratch resistance.

In the above Examples, embodiments are shown in which zirconium has beenadopted as the metal constituting the oxide. However, tantalum is metalthat is known to permit the formation of oxide films of identical orsimilar film properties to those of zirconium oxide films. Accordingly,an aspect of the present invention can provide eyeglass lenses with Taoxide films having high heat resistance and good scratch resistance.

No crystal lattices were found in the planar TEM images obtained atmagnifications of 400,000-fold of the vapor-deposited films prepared inExamples 1 to 3. By contrast, a slight crystal lattice was found inComparative Example 1 and an extensive crystal lattice was found inComparative Example 2.

FIG. 3 is a cross-sectional TEM image obtained in the evaluation ofExample 1. FIG. 4 is a planar TEM image obtained for Example 1.

FIG. 5 is a cross-sectional TEM image obtained in the evaluation ofExample 2. FIG. 6 is a planar TEM image obtained for Example 2.

FIG. 7 is a cross-sectional TEM image obtained in the evaluation ofExample 3. FIG. 8 is a planar TEM image obtained for Example 3.

FIG. 9 is a planar TEM image obtained in the evaluation of ComparativeExample 1.

FIG. 10 is a cross-sectional planar TEM image obtained in the evaluationof Comparative Example 2. FIG. 11 is a planar TEM image obtained forComparative Example 2.

FIG. 12 is an enlarged view of the planar TEM image shown in FIG. 11with some of the grains in a frame.

A comparison of the drawings clearly reveals that the vapor-depositedfilms fabricated in Comparative Examples 1 and 2 were less uniform thanthe vapor-deposited films fabricated in Examples 1 to 3.

[Specific Embodiments Relating to Determining Manufacturing Conditions]

1. Determining Candidate Vapor Deposition Conditions

Using ZrO₂ as a vapor deposition source, ZrO₂ vapor-deposited films wereformed to film thicknesses of about 70 nm by an ion-assisted methodunder varying ion-assisted conditions (condition 1, condition 2) onglass substrates. The current and voltage of the ion gun were set higherin condition 2 than in condition 1.

2. Evaluation of Uniformity of TEM Image

For each of the ZrO₂ vapor-deposited films fabricated by vapordeposition under condition 1 in 1. above and the ZrO₂ vapor-depositedfilms fabricated by vapor deposition under condition 2, a piece of dummyglass was adhered with an adhesive to the ZrO₂ vapor-deposited film fromabove and a sample was cut in the sectional direction of the ZrO₂vapor-deposited film. Etching by ion milling was used to shave down theZrO₂ vapor-deposited film in the sectional direction. The etching wasstopped when the thickness of the ZrO₂ vapor-deposited film reachedabout 100 nm. The sample thus fabricated was placed in a transmissionelectron microscope and a cross-sectional image (bright-field image) wasobtained at a magnification of 150,000-fold.

For each cross-sectional TEM image, commercial analysis software wasused to binary process the shade of a region 130 nm×130 nm in area andthe area fractions of the dark portions and bright portions wereobtained. As a result, the value of the ZrO₂ vapor-deposited filmfabricated by vapor deposition under condition 2 was greater than thevalue of the ZrO₂ vapor-deposited film fabricated by vapor depositionunder condition 1.

The absence or presence of the region the major axis length of which asan actual size was equal to or more than 1 nm was determined in an areameasuring 130 nm×130 nm. As a result, the cross-sectional TEM image ofthe ZrO₂ vapor-deposited film fabricated by vapor deposition undercondition 2 was determined not to have such a region.

By contrast, columnar structures with a major axis length of equal to ormore than 1 nm as an actual size were found in the cross-sectional TEMimage of the ZrO₂ vapor-deposited film fabricated by vapor depositionunder condition 1. In the ZrO₂ vapor-deposited film fabricated by vapordeposition under condition 1, multiple columnar structures with majoraxis lengths of 2 nm to 40 nm and minor axis lengths of 0.5 nm to 2 nmas an actual size were observed.

3. Evaluation of heat resistance

A ZrO₂ vapor-deposited film formed on a plastic lens substrate (productname Eyas, made by HOYA Corp., refractive index 1.6, colorless lens) bythe same method as in 1. above was placed for two hours in a heatingfurnace at the internal furnace temperature shown in Table 4, afterwhich the presence of cracks several cm or more in length in the ZrO₂vapor-deposited film was evaluated under a fluorescent lamp. Thepresence of cracks was denoted by X and the absence of cracks wasdenoted by ∘. The results are given in Table 2.

TABLE 2 Internal temperature Presence of cracks in ZrO₂ Presence ofcracks in ZrO₂ of heating vapor-deposited film vapor-deposited filmfurnace formed under condition 1 formed under condition 2 80° C. x ∘ 85°C. x ∘ 90° C. x ∘ 95° C. x ∘ 100° C. x ∘

Based on the above results, it was determined that the greater theuniformity of the cross-sectional TEM image, the better the heatresistance of the vapor-deposited film.

4. Measurement of Film Stress

By the same method as set forth above, ZrO₂ vapor-deposited films wereformed on the surface of cover glasses under condition identical toconditions 1 and 2. When the film stress was measured, tensile stresswas present under condition 1 and compressive stress under condition 2.

5. Evaluation of Scratch Resistance

A water-repellent film in the form of a fluorine-substituted alkylgroup-comprising organic silicon compound made by Shin-Etsu ChemicalCo., Ltd., KY130, was vapor deposited by halogen heating on a ZrO₂vapor-deposited film formed on a plastic lens substrate (product nameEyas, made by HOYA Corp., refractive index 1.6, colorless lens) by thesame method as in 1. above and samples were prepared.

The samples thus prepared were subjected to a scratch resistance test byrunning steel wool back and forth 20 times with a load of 1 kg, and ascratch resistance test by running a sand eraser back and forth 5 timeswith a load of 3 kg. Following the scratch tests, the ZrO₂vapor-deposited film was observed under a fluorescent lamp and thepresence or absence of scratches and cracks 5 mm or greater in lengthwas determined. For six or more scratches or cracks, the scratchresistance was evaluated as X, five or fewer but equal to or more than 2as A, and one or none as ∘.

6. Measurement of Film Hardness (Indentation Hardness)

ZrO₂ vapor-deposited films were formed on plastic lens substrates(product name Eyas, made by HOYA Corp., refractive index 1.6, colorlesslens) under conditions 1 and 2 by the same method as in 1. above.

The indentation hardness of the ZrO₂ vapor-deposited film that wasformed was measured by the following method with a measuring apparatus(Elionix ultra-micro indentation hardness tester ENT-2100).

In measurement, a triangular pyramid diamond indenter with an edgeinterval of 115 degrees was employed. Measurement conditions were set inthe form of an indenter load rate of 0.2 mgf/sec, a maximum load of 0.98mN maintained for 1 sec, followed by unloading at the same load rate.The indentation depth at maximum load was read from an indenterindentation depth—load curve obtained by this measurement.

The indentation hardness H was calculated from the following equation.H=P _(max) /A(h _(A))  (1)

In the above equation, P_(max) denotes the maximum load, A(h_(A))denotes the projected contact area of the indenter. A (h_(A)) wasobtained by first obtaining h_(A) from the maximum indentation depthh_(max) and the intersection h_(s) of the unloading curve gradient andthe displacement axis, and then from the geometric shape (vertical angle65.03°) of the regular triangular pyramide (Berkovich type) indentercomprised of diamond. The equations for h_(A) and A (h_(A)) are bothgiven below:h _(A) =h _(max)−0.75(h _(max) −h _(s))  (2)A(h _(A))=3√3 tan²(65.03°)h _(A) ²  (3)(In this context, 0.75 in equation (2) is a constant of a Berkovich typeindenter.)

In the measurement results, the indentation hardness of the ZrO₂vapor-deposited film formed under condition 2 achieved a higher valuethan the indentation hardness of the ZrO₂ vapor-deposited film formedunder condition 1.

The above results are given in Table 3.

TABLE 3 Presence of cracks in Presence of cracks in ZrO₂ vapor- ZrO₂vapor-deposited deposited film formed film formed under under condition1 condition 2 Scratch resistance test by x ∘ running steel wool back andforth 20 times at a load of 1 kg Scratch resistance test by Δ ∘ runningsand eraser back and forth 5 times at a load of 3 kg Indentationhardness low high

From the above results, it was determined that the higher the uniformityof the cross-sectional TEM image, the better the scratch resistance ofthe vapor-deposited film. The fact that vapor deposition conditionpermitting the fabrication of vapor-deposited films with good scratchresistance can be determined by the simple method of image analysiswithout requiring stress or hardness measurement in this manner is oneof the advantages afforded by an aspect of the present invention.

When the proportion of the observed field accounted for by regions in alump shape observed in the cross-sectional TEM image by the method setforth above was obtained for the ZrO₂ vapor-deposited film fabricatedunder condition 1 and the ZrO₂ vapor-deposited film fabricated undercondition 2, that of the ZrO₂ vapor-deposited film fabricated undercondition 2 was equal to or less than 20% and that of the ZrO₂vapor-deposited film fabricated under condition 1 exceeded 20%.

When the average grain size and grain boundary occupancy rate observedin the planar TEM images by the method set forth above were obtained forthe ZrO₂ vapor-deposited film fabricated under condition 1 and the ZrO₂vapor-deposited film fabricated under condition 2, the average grainsize was larger and the grain boundary occupancy rate was lower in theZrO₂ vapor-deposited film fabricated under condition 2 than in the ZrO₂vapor-deposited film fabricated under condition 1.

7. Preparation of Eyeglass Lenses

A total of 8 layers of vapor-deposited films, shown in Table 4 below,were sequentially formed by an ion-assisted method using an assist gasin the form of oxygen gas or a mixed gas of oxygen and argon on thesurface of a hard coat on the convex side of a plastic lens substrate(product name Eyas, made by HOYA Corp., refractive index 1.6, colorlesslens) having a convex surface on the object side and a concave surfaceon the eyeball side, with both sides having been optically finished andcoated with hard coats in advance. After forming the 8th vapor-depositedfilm, a 9th layer film in the form of a water-repellent layer was formedover it by vapor deposition by halogen heating using a vapor depositionsource in the form of KY130, which is a fluorine-substituted alkylgroup-comprising organic silicon compound made by Shin-Etsu ChemicalCo., Ltd. Two types (eyeglass lenses 1 and 2) were prepared. During thefabrication of eyeglass lens 1, above condition 1 was employed as thevapor deposition condition of the ZrO₂ vapor-deposited film. During thefabrication of eyeglass lens 2, above condition 2 was employed as thevapor deposition condition of the ZrO₂ vapor-deposited film. The othermanufacturing conditions were identical.

TABLE 4 Vapor Film thickness deposition source (nm) 1^(st) layer SiO₂ 302^(nd) layer ZrO₂ 10 3^(rd) layer SiO₂ 200 4^(th) layer ITO 10 5^(th)layer ZrO₂ 30 6^(th) layer SiO₂ 20 7^(th) layer ZrO₂ 60 8^(th) layerSiO₂ 90

8. Heat Resistance Test of Eyeglass Lens Samples

The eyeglass lenses fabricated in 7. above were placed for 1 hour in a100° C. oven, held up to a fluorescent lamp, and visually evaluated forthe presence of cracks. As a result, the eyeglass lens 1 that had beenfabricated with the ZrO₂ vapor-deposited film under condition 1exhibited many cracks running several cm in length in the ZrO₂vapor-deposited film, but the eyeglass lens 2 that had been fabricatedwith the ZrO₂ vapor-deposited film under condition 2 afforded a highdegree of transparence and did not exhibit cracks.

9. Scratch Resistance Test of Eyeglass Lens Samples

The eyeglass lenses fabricated in 7. above were subjected to a scratchresistance test by running steel wool back and forth 20 times with aload of 1 kg, and a scratch resistance test by running a sand eraserback and forth 5 times with a load of 3 kg. As a result, the eyeglasslens that had been fabricated with the ZrO₂ vapor-deposited film undercondition 1 exhibited several scratches and cracks, but the eyeglasslens fabricated with the ZrO₂ vapor-deposited film under condition 2afforded a high degree of transparence and did not develop scratches orcracks.

Based on the results of 8. and 9., the fabrication of ZrO₂vapor-deposited films under vapor deposition conditions determined to begood for heat resistance and scratch resistance based on the uniformityof the TEM image was confirmed to yield eyeglass lenses having gooddurability and scratch resistance. Conventionally, the discovery ofvapor deposition conditions permitting the forming of vapor-depositedfilms with good heat resistance and scratch resistance would requirerepeatedly implementing an accelerated durability test such as the ovenheating implemented in 8. above, implementing the scratch resistancetests on eyeglass lens samples that was implemented in 9 above, andselecting candidate conditions. By contrast, an aspect of the inventionmakes it possible to determine manufacturing conditions permitting themanufacturing of eyeglass lenses having good durability by the simplemethod of fabricating test vapor-deposited films as well as obtainingthe TEM images thereof and evaluating the uniformity.

INDUSTRIAL APPLICABILITY

The present invention is useful in the field of manufacturing eyeglasslenses.

The invention claimed is:
 1. An eyeglass lens comprising a lenssubstrate and a vapor-deposited film either directly or indirectly onthe lens substrate, wherein the vapor-deposited film is an oxide film ofzirconium, with a proportion accounted for by columnar structure orcrystalline grains observed in a cross-sectional image of thevapor-deposited film obtained by a transmission electron microscope offrom 2% to 20% based on the entire area of the observed field, which isset to 100 nm square (100 nm × 100 nm) to 150 nm square (150 nm × 150nm) at a magnification of 100,000 to 200,000-fold, or 50 nm square (50nm × 50 nm) to 100 nm square (100 nm × 100 nm) at a magnification ofexceeding 200,000-fold; an average grain size of the vapor-depositedfilm observed in a planar image obtained by a transmission electronmicroscope ranges from 5 nm to 20 nm; and a film stress of thevapor-deposited film ranges from −200 MPa to 50 MPa.
 2. The eyeglasslens according to claim 1, wherein the columnar structure or crystallinegrains comprise an amorphous material.
 3. The eyeglass lens according toclaim 1, wherein the proportion accounted for by the columnar structureor crystalline grains is equal to or less than 15% based on the entirearea of the observed field.
 4. The eyeglass lens according to claim 1,wherein the proportion accounted for by the columnar structure orcrystalline grains is equal to or less than 10% based on the entire areaof the observed field.
 5. The eyeglass lens according to claim 1,wherein a proportion accounted for by grain boundaries, which areboundaries separating grains from regions outside of the grains, in aplanar image obtained by a transmission electron microscope is less than10% based on the entire area of the observed field.
 6. The eyeglass lensaccording to claim 1, which comprises the vapor-deposited film as atleast one layer in a multilayer vapor-deposited film.
 7. The eyeglasslens according to claim 1, wherein the proportion accounted for by thecolumnar structure or crystalline grains is from 2% to 15% based on theentire area of the observed field.
 8. The eyeglass lens according toclaim 1, wherein the proportion accounted for by the columnar structureor crystalline grains is from 2% to 10% based on the entire area of theobserved field.
 9. The eyeglass lens according to claim 1, wherein aproportion accounted for by grain boundaries, which are boundariesseparating grains from regions outside of the grains, in a planar imageobtained by a transmission electron microscope is from 1% to 5% based onthe entire area of the observed field.
 10. The eyeglass lens accordingto claim 1, wherein an average grain size of the vapor-deposited filmobserved in a planar image obtained by a transmission electronmicroscope ranges from 5.8 nm to 11.5 nm.